Edwin Howard Armstrong. Historical portrait of the American radio engineer Edwin Howard Armstrong (1890-1954). During the First World War, Armstrong worked on locating aircraft by their stray radio emissions. This work led to the development of the superheterodyne circuit which made radio tuning much easier. By 1939 he had developed frequency modulation (FM) radio transmission which virtually eliminated the static that plagued amplitude modulation (AM) transmissions. Many of his inventions became universally adopted, but he was a contentious man, forever engaged in lawsuits. He eventually took his own life in a fit of depression.